fix: fill/rename LastVerified -> LastUpdated in replica

[elijaharita]

this PR also includes a fix for a bug my last PR introduced where preparation job loop immediately closes on startup

closes #132
closes #137

[masih]

Also update the open API spec?

[elijaharita]

@masih ah, didn't know we had this. good to know, i'll do that

[elijaharita]

also, i will wait for integration test to merge, it fixes a bug that will allow ci to pass

[masih]

@elijaharita the integration test PR is now merged, this PR should be good to go?

[codecov-commenter]

Codecov Report

Merging #136 (0f557e6) into main (c38b9f6) will decrease coverage by 0.13%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #136      +/-   ##
==========================================
- Coverage   31.83%   31.70%   -0.13%     
==========================================
  Files           5        5              
  Lines         735      738       +3     
==========================================
  Hits          234      234              
- Misses        466      469       +3     
  Partials       35       35              

Files	Coverage Δ
blob/blob.go	37.50% <ø> (ø)
integration/singularity/store.go	36.76% <0.00%> (-0.25%)	⬇️